DE102019220303A1 - Pressure-sensitive adhesive for bonding paper - Google Patents

Abstract

The aim is to provide a repulpable pressure-sensitive adhesive which can be used well on both polar and non-polar papers and is stable in storage. This is achieved with a pressure-sensitive adhesive comprising at least one polymer, the underlying monomer composition of which is a) 10 to 30% by weight of at least one compound according to the formula (I) CH2 = CH-C (O) NR1R2 (I), where R1 is an unsubstituted alkyl group, a hydroxyalkyl group or an acronyl radical and R2 represents a hydrogen atom, an unsubstituted alkyl group, a hydroxyalkyl group, an acetonyl radical or an aminoalkyl group; b) 60 to 80% by weight of at least one compound according to the formula (II) CH2 = CH-C (O) O- (CH2) 2-O-R3 (II), where R3 represents an unsubstituted alkyl group, an alkoxyalkyl group or a (polyalkoxy) alkyl group; andc) 0.5 to 10% by weight of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid and (C2-C4-hydroxyalkyl) acrylates. The invention also relates to an adhesive tape which comprises such a pressure-sensitive adhesive and the use a pressure-sensitive adhesive according to the invention and / or an adhesive tape according to the invention for producing water-soluble bonds.

Description

The invention relates to the technical field of pressure-sensitive adhesives, as they are often used in technology for the temporary and permanent bonding of substrates. More specifically, the invention proposes a pressure-sensitive adhesive based on a special poly (meth) acrylate, which is particularly suitable for bonding paper and, moreover, for producing washable bonds.

Pressure-sensitive adhesives are widely used both in the production and in the use of papers. Essential applications are, for example, in roll changes when processing large paper rolls; here, pressure-sensitive adhesives are used in what are known as splicing tapes in order to enable an uncomplicated change from one roll to the next that is as quick as possible, and thus a continuous process. In addition, permanent splices that remain temporarily or permanently in the paper are also used. The paper is often glued to the roll core at the beginning of the winding process (so-called core starting), or the outer layer of paper rolls is fixed with an adhesive tape during storage or transport (so-called end tabbing).

In paper production and paper processing, high demands are made on the pressure-sensitive adhesives used there. The masses should often have a high tack - just think of the flying roll change, where the short contact time between the running and the newly introduced roll must be sufficient to build up a bond between the two paper webs that withstands the shear forces prevailing at the web speed and is ultimately stronger than the splitting force required to open the roll lock (split labels, so-called butterflies) or the splitting system integrated in the adhesive tape.

Of course, the PSAs should also generally have high bond strengths which develop both on polar and on less polar papers. For permanent bonds in particular, high aging stability is required, which is expressed, for example, in a high resistance to calcium ions migrating from white coated paper or paper filled _{with CaCO 3.} From the point of view of sustainability, it is often necessary for the adhesives to be redetachable from the paper substrate, at least in water (repulpability).

The aspect of the redetachability of a pressure-sensitive adhesive from the substrate to be bonded is also of particular interest in technical areas outside of the paper industry; For example, this is also an increasingly common requirement for the bonding of batteries or rechargeable batteries in electronic devices such as cell phones etc.

There has therefore been no lack of attempts to provide pressure-sensitive adhesives which satisfy the profile of requirements described.

• i.a) 50 bis 89,5 Gew.-% zumindest einen Acrylsäureester und/oder Methacrylsäureester mit der folgenden Formel: CH₂=C(R₁)(COOR₂), wobei R₁ = H und R₂ ein linearer Alkylrest mit 2 bis 10 C-Atomen oder ein verzweigter, nichtcyclischer Alkylrest mit mindestens 4 C-Atomen ist und/oder R₁ = CH₃ und R₂ ein linearer Alkylrest mit 8 bis 10 C-Atomen oder ein verzweigter, nichtcyclischer Alkylrest mit mindestens 10 C-Atomen ist,
• i.b) 5 bis 20 Gew.-% zumindest ein N-Alkyl-substituiertes Acrylamid
• i.c) 5 bis 25 Gew.-% zumindest ein Acrylsäureester und/oder Methacrylsäureester mit der folgenden Formel: CH₂=C(R₃)(COOR₄), wobei R₃ = H oder CH₃ und R₄ ein linearer Alkylrest mit mindestens 12 C-Atomen ist;
• i.d) 0,5 bis 5 Gew.-% Acrylsäure und/oder Methacrylsäure, wobei die Mengenangaben jeweils auf die Monomermischung bezogen sind und diese Haftklebmasse für die Verklebung flexibler Druckplatten vorgesehen ist.

WO 2014/001096 A1 describes a pressure-sensitive adhesive comprising at least one polymer component based on a monomer mixture comprising at least the following monomers:

• ia) 50 to 89.5% by weight of at least one acrylic acid ester and / or methacrylic acid ester with the following formula: CH ₂ = C (R ₁ ) (COOR ₂ ), where R ₁ = H and R _{2 is} a linear alkyl radical with 2 to 10 carbon atoms or a branched, non-cyclic alkyl radical with at least 4 carbon atoms and / or R ₁ = CH ₃ and R _{2 is} a linear alkyl radical with 8 to 10 carbon atoms Atoms or a branched, non-cyclic alkyl radical with at least 10 carbon atoms,
• ib) 5 to 20% by weight of at least one N-alkyl-substituted acrylamide
• ic) 5 to 25% by weight of at least one acrylic acid ester and / or methacrylic acid ester with the following formula: CH ₂ = C (R ₃ ) (COOR ₄ ), where R ₃ = H or CH ₃ and R _{4 is} a linear alkyl radical with at least 12 carbon atoms;
• id) 0.5 to 5% by weight of acrylic acid and / or methacrylic acid, the amounts stated in each case being based on the monomer mixture and this pressure-sensitive adhesive being intended for bonding flexible printing plates.

WO 95/14746 A2 relates to a water-soluble or water-dispersible pressure-sensitive adhesive which comprises a normally tacky copolymer of a water-soluble base monomer and a water-dispersible macromer.

1. a) 65 - 95 Gew.-% einer Vinylcarbonsäure,
2. b) 5 -35 Gew.-% eines Alkyl(meth)acrylsäureesters mit 1-12 C-Atomen im Alkylrest und
3. c) 0,05-5,0 Gew.-% eines polymerisationsfähigen Fotoinitiators

und
30 bis 150 gew.-Teile eines wasserlöslichen Weichmachers mit einer Molmasse bis 4.000 Dalton. EP 0 699 726 A2 discloses a water-soluble pressure-sensitive adhesive containing
100 parts by weight of a water-soluble copolymer

1. a) 65-95% by weight of a vinyl carboxylic acid,
2. b) 5-35% by weight of an alkyl (meth) acrylic acid ester with 1-12 carbon atoms in the alkyl radical and
3. c) 0.05-5.0% by weight of a polymerizable photoinitiator

and
30 to 150 parts by weight of a water-soluble plasticizer with a molecular weight of up to 4,000 Daltons.

EP 1 489 153 A1 describes a repulpable pressure-sensitive adhesive which comprises at least one block copolymer based on polyacrylate.

There is a continuing need for adhesive tapes with a good profile of properties for bonding paper. The object of the invention was to provide a repulpable pressure-sensitive adhesive which can be used well on both polar and non-polar papers and is stable in storage.

1. a) 10 bis 30 Gew.-% mindestens einer Verbindung gemäß der Formel (I) CH₂=CH-C(O)NR¹R² (I), worin R₁ für eine unsubstituierte Alkylgruppe, eine Hydroxyalkylgruppe oder einen Acetonylrest und R₂ für ein Wasserstoffatom, eine unsubstituierte Alkylgruppe, eine Hydroxyalkylgruppe, einen Acetonylrest oder eine Aminoalkylgruppe stehen;
2. b) 60 bis 80 Gew.-% mindestens einer Verbindung gemäß der Formel (II) CH₂=CH-C(O)O-(CH₂)₂-O-R³ (II), worin R³ für eine unsubstituierte Alkylgruppe, eine Alkoxyalkylgruppe oder eine (Polyalkoxy)alkylgruppe steht; und
3. c) 0,5 bis 10 Gew.-% mindestens eines Monomers ausgewählt aus der Gruppe bestehend aus Acrylsäure, Methacrylsäure und (C₂-C₄-Hydroxyalkyl)(meth)acrylaten

umfasst. Wie sich gezeigt hat, weisen derartige Haftklebmassen neben einer guten Repulpierbarkeit einen hohen Tack auf und zeigen hohe Klebkräfte auf verschiedenen Papieren sowie gute Scherfestigkeiten. Zudem zeigen sie eine geringe Neigung, in Papier hinein zu migrieren, und haben sich als widerstandsfähig gegen das Einwandern von Calcium-Ionen erwiesen.The solution to the problem is based on the idea of using a poly (meth) acrylate with a specific underlying monomer composition in a pressure-sensitive adhesive. A first and general subject of the invention is thus a pressure-sensitive adhesive which contains at least one polymer, its underlying monomer composition

1. a) 10 to 30% by weight of at least one compound according to the formula (I) CH ₂ = CH-C (O) NR ¹ R ² (I), wherein R _{1 represents} an unsubstituted alkyl group, a hydroxyalkyl group or an acetonyl radical and R _{2 represents} a hydrogen atom, an unsubstituted alkyl group, a hydroxyalkyl group, an acetonyl radical or an aminoalkyl group;
2. b) 60 to 80% by weight of at least one compound according to the formula (II) CH ₂ = CH-C (O) O- (CH ₂ ) ₂ -OR ³ (II), wherein R ^{3 represents} an unsubstituted alkyl group, an alkoxyalkyl group or a (polyalkoxy) alkyl group; and
3. c) 0.5 to 10% by weight of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid and (C ₂ -C ₄ -hydroxyalkyl) (meth) acrylates

includes. It has been found that, in addition to good repulpability, such PSAs have a high tack and show high bond strengths on various papers and good shear strengths. In addition, they have a low tendency to migrate into paper and have proven to be resistant to the migration of calcium ions.

According to the invention, a pressure-sensitive adhesive or a pressure-sensitive adhesive is understood, as is customary in common parlance, to be a substance which is permanently tacky and tacky at least at room temperature. It is characteristic of a pressure-sensitive adhesive that it can be applied to a substrate by pressure and remains adhered there, the pressure to be applied and the duration of this pressure not being defined in more detail. In general, but basically depending on the exact type of pressure-sensitive adhesive as well as the substrate, the temperature and the air humidity, a short-term, minimal effect is sufficient Pressure that does not go beyond a light touch for a short moment in order to achieve the adhesive effect, in other cases a longer-term exposure to a higher pressure may be necessary.

Pressure-sensitive adhesives have special, characteristic viscoelastic properties which lead to permanent tack and adhesiveness. They are characterized by the fact that when they are mechanically deformed, both viscous flow processes and the build-up of elastic restoring forces occur. With regard to their respective proportions, the two processes are in a certain relationship to one another, depending both on the precise composition, the structure and the degree of crosslinking of the PSA and on the speed and duration of the deformation and on the temperature.

The proportionate viscous flow is necessary to achieve adhesion. Only the viscous components, often caused by macromolecules with relatively high mobility, enable good wetting and flow onto the substrate to be bonded. A high proportion of viscous flow leads to high pressure-sensitive tack (also referred to as tack or surface tack) and thus often also to high adhesion. Strongly cross-linked systems, crystalline or glass-like solidified polymers are generally not or at least only slightly tacky due to the lack of flowable components.

The proportional elastic restoring forces are necessary to achieve cohesion. They are caused, for example, by very long-chain and strongly tangled macromolecules, as well as by physically or chemically cross-linked macromolecules and enable the forces acting on an adhesive bond to be transmitted. They lead to the fact that an adhesive connection can withstand a permanent load acting on it, for example in the form of permanent shear stress, to a sufficient extent over a longer period of time.

The storage modulus (G ') and loss modulus (G' ') that can be determined by means of dynamic mechanical analysis (DMA) are used for a more precise description and quantification of the degree of elastic and viscous components as well as the relationship between the components. G 'is a measure of the elastic part, G' 'is a measure of the viscous part of a substance. Both sizes are dependent on the deformation frequency and the temperature.

The sizes can be determined with the aid of a rheometer. The material to be examined is exposed to a sinusoidally oscillating shear stress, for example in a plate-plate arrangement. In devices controlled by shear stress, the deformation is measured as a function of time and the time offset of this deformation with respect to the introduction of the shear stress. This time offset is referred to as the phase angle δ.

The storage modulus G 'is defined as follows: G' = (τ / γ) · cos (δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector). The definition of the loss modulus G '' is: G '' = (τ / γ) · sin (δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between the shear stress and deformation vector).

In particular, a mass is considered a pressure-sensitive adhesive and is defined as such in the context of the invention, if at 23 ° C in the deformation frequency range of 10 ° to 10 ¹ rad / sec both G 'and G''are at least partially in the range of 10 ³ to 10 ⁷ Pa. “Partly” means that at least a section of the G 'curve lies within the window that is defined by the deformation frequency range from 10 ° up to and including 10 ¹ rad / sec (abscissa) and the range of G' values from 10 ³ up to and including 10 ⁷ Pa (ordinate), and if at least a section of the G ″ curve is also within the corresponding window.

According to the invention, the monomer composition of the polymer comprises 10 to 30% by weight of at least one compound according to the formula (I) CH ₂ = CH-C (O) NR ¹ R ² (I), wherein R _{1 represents} an unsubstituted alkyl group, a hydroxyalkyl group or an acetonyl radical and R _{2 represents} a hydrogen atom, an unsubstituted alkyl group, a hydroxyalkyl group, an acetonyl radical or an aminoalkyl group. If several such monomers are contained, the monomer composition comprises monomers a) to a total of 10 to 30 wt .-%. The weight fraction range according to the invention for the monomers a) ensures, in particular, good tack of the PSA and its good repulpability. The monomer composition of the polymer preferably comprises 15 to 28% by weight of at least one compound according to the formula (I). If several monomers of this type are contained, the monomer composition comprises monomers a) preferably in a total of 15 to 28% by weight.

The compound according to the formula (I) is preferably selected from the group consisting of N-methylacrylamide, N-ethylacrylamide, N-hydroxyethylacrylamide, diacetonylacrylamide, N-isopropylacrylamide, N-ethyl-N-aminoethylacrylamide, N-ethyl-N-hydroxyethylacrylamide, N, N-dimethylacrylamide, N, N-dihydroxymethylacrylamide, N, N-diethylacrylamide, N, N-dihydroxyethylacrylamide.

In one embodiment, R ₁ and R ₂ independently of one another represent an unsubstituted alkyl group; the compound according to the formula (I) N, N-dimethylacrylamide is particularly preferred.

The compound according to the formula (II) is preferably selected from the group consisting of methyl diglycol acrylate, ethyl diglycol acrylate, 2-ethoxyethyl acrylate, 2-methoxyethyl acrylate and methoxypolyethylene glycol acrylate. The compound according to the formula (II) ethyl diglycol acrylate is particularly preferred.

If several monomers according to the formula (II) are present, the monomer composition comprises monomers b) to a total of 60 to 80% by weight.

The monomer composition preferably comprises as monomer c) at least acrylic acid or 2-hydroxyethyl acrylate. If several monomers c) are contained, the monomer composition comprises monomers c) in a total of 0.5 to 10% by weight.

The monomer composition on which the polymer of the pressure-sensitive adhesive of the invention is based can moreover comprise up to 10% by weight of alkyl acrylates having 1 to 4 carbon atoms in the alkyl radical.

1. a) 10 bis 30 Gew.-% N,N-Dimethylacrylamid;
2. b) Ethyldiglycolacrylat und/oder2-Ethoxyethylacrylat zu insgesamt 60 bis 80 Gew.-%; und
3. c) Acrylsäure und/oder 2-Hydroxyethylacrylat zu insgesamt 0,5 bis 10 Gew.-%,

wobei die Gewichtsanteile selbstverständlich jeweils auf das Gesamtgewicht der Monomerenzusammensetzung bezogen sind.In one embodiment, the monomer composition on which the polymer of the pressure-sensitive adhesive of the invention is based comprises

1. a) 10 to 30% by weight of N, N-dimethylacrylamide;
2. b) ethyl diglycol acrylate and / or 2-ethoxyethyl acrylate to a total of 60 to 80% by weight; and
3. c) acrylic acid and / or 2-hydroxyethyl acrylate to a total of 0.5 to 10% by weight,

the proportions by weight of course being based in each case on the total weight of the monomer composition.

The polymer of the pressure-sensitive adhesive of the invention is preferably crosslinked. The polymer is particularly preferably thermally crosslinked. Thermal crosslinking can be carried out under considerably milder conditions than, for example, radiation-induced crosslinking, which can occasionally also have a destructive effect. According to the invention, however, it is also possible to effect crosslinking of the polyacrylate exclusively or additionally by actinic radiation, it being possible to add necessary or promoting crosslinking substances, e.g. UV crosslinkers, if necessary.

The polymer of the pressure-sensitive adhesive of the invention is therefore preferably thermally crosslinked, i.e. by means of substances which, under the influence of thermal energy, enable (initiate) and / or promote a crosslinking reaction. Preferred thermal crosslinkers are coordinative crosslinkers; the polymer is particularly preferably thermally crosslinked with one or more metal chelates, in particular with at least one aluminum chelate and / or at least one titanium chelate.

The coordinative crosslinkers, in particular aluminum chelates, are preferably used in an amount of 0.1 to 1 part by weight, particularly preferably 0.2 to 0.8 part by weight, based in each case on 100 parts by weight of the polymer (solvent-free ), used. In one variant, the coordinative crosslinkers, in particular titanium chelates, are preferably used in an amount of 1 to 4 parts by weight, particularly preferably 1.7 to 3.3 parts by weight, based in each case on 100 parts by weight of the polymer ( solvent-free).

The polymer is very particularly preferably crosslinked with aluminum acetylacetonate or titanium diisopropoxide bis (acetylacetonate).

In principle, all free-radical or free-radical-controlled polymerizations, as well as combinations, can be used to produce the polymers of the pressure-sensitive adhesive of the invention different polymerization processes. In addition to the conventional, free radical polymerization, these are z. B. also the ATRP, the nitroxide / TEMPOcontrolled polymerization or the RAFT process. Preferred solvents for the polymerization are water, acetone, isopropanol, ethanol and ethyl acetate and any mixtures thereof.

The polymer of the pressure-sensitive adhesive according to the invention preferably has a weight-average molar mass M _w of 300,000 to 2,000,000 g / mol.

In one embodiment, the pressure-sensitive adhesive of the invention contains at least one adhesive resin. Tackifying resins, also referred to as tackifying resins, are often admixed with pressure-sensitive adhesives in order to fine-tune the pressure-sensitive adhesive properties.

“Resins” are understood to mean, in particular, those oligo- and (low) polymeric compounds whose number-average molar mass M _{n is} not more than 5,000 g / mol. It goes without saying that short-chain polymerization products that arise during the polymerization to produce the polymer of the pressure-sensitive adhesive according to the invention are not subsumed under the term “resins”.

Tackifying resins often have softening points in the range from 80 to 150 ° C. The information on the softening point T _E of oligomeric and polymeric compounds, such as resins, relate to the ring-ball method in accordance with DIN EN 1427: 2007 when the provisions are applied accordingly (examination of the oligomer or polymer sample instead of bitumen if otherwise retained procedure). The measurements are carried out in a glycerol bath.

In one embodiment, the pressure-sensitive adhesive of the invention contains at least one adhesive resin selected from the group consisting of rosin and rosin derivatives such as rosin esters, also by, for. B. disproportionation or hydrogenation stabilized rosin derivatives; Terpene phenolic resins; Acrylate resins and sugar resins.

The PSA of the invention preferably contains tackifier resins in a total of at most 30% by weight. It can contain one or more tackifier resins.

However, the pressure-sensitive adhesive of the invention is preferably free from tackifier resins.

To optimize the properties of the PSA of the invention, it can also contain other common additives such as fillers, for example electrically conductive filler materials, thermally conductive filler materials and the like, or flame retardants, for example ammonium polyphosphate and its derivatives.

If the pressure-sensitive adhesive of the invention is to be colored, it can also contain water-soluble pigments or other dyes.

The pressure-sensitive adhesive according to the invention can moreover also be in foamed form and contain corresponding blowing agents, in particular blowing gases; Micro-bodies, in particular hollow micro-spheres, made, for example, of glass, ceramic or fly ash; contain expandable or expanded hollow microspheres with a thermoplastic polymer shell and the like.

The invention further provides an adhesive tape which comprises a pressure-sensitive adhesive of the invention.

The general term "adhesive tape" in the context of this invention includes all flat structures such as films or film sections, papers or paper sections, tapes with extended length and limited width, tape sections, labels, which are extended in two dimensions, at least on one side and over the entire surface or partially with pressure-sensitive adhesive. Die cuts and the like.

In the simplest case, an inventive adhesive tape consists only of an inventive pressure-sensitive adhesive (adhesive transfer tape). In order to be able to apply the adhesive tape rolled up into a cup roll or cross-wound into a spool without it sticking to itself, the pressure-sensitive adhesive is preferably covered with at least one release liner.

In addition to a pressure-sensitive adhesive of the invention, an adhesive tape according to the invention can also comprise at least one carrier and optionally also further layers, for example further pressure-sensitive adhesive layers, further reinforcing carrier layers, etc.

In one embodiment, the adhesive tape comprises a carrier and a layer of a pressure-sensitive adhesive of the invention. The material of the carrier is preferably selected from the group consisting of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and paper. In particular, the material of the carrier is paper.

In the embodiment with a carrier, the adhesive tape according to the invention can be configured as a single-sided or double-sided adhesive tape. Furthermore, the adhesive tape according to the invention can also be designed as a cleavable adhesive tape.

In the embodiment with a carrier, too, at least one pressure-sensitive adhesive of the adhesive tape is preferably covered with a release liner in order to enable problem-free unwinding and to protect the pressure-sensitive adhesive (s) from soiling. Release liners usually consist of a plastic film siliconized on one or both sides (e.g. PET or PP) or a siliconized paper carrier. They are not included in the adhesive tape, but are only temporarily connected to it as an aid.

In an adhesive tape of the invention, the pressure-sensitive adhesive of the invention is particularly preferably covered with a repulpable release liner.

The invention further provides the use of a pressure-sensitive adhesive of the invention and / or of an adhesive tape of the invention for producing water-soluble bonds. “Water-soluble bonds” are bonds in which, under the influence of water, the bonded substrates can be detached from one another with a manageable and technically sensible expenditure of time and equipment. The term does not include that the pressure-sensitive adhesive or the adhesive tape can be removed from the substrate without leaving any residue. Preferably, however, the pressure-sensitive adhesive of the invention can be removed without residue from a substrate bonded to it. Preferred substrates in this context are papers and components of battery cells.

The invention further provides the use of a pressure-sensitive adhesive of the invention and / or of an adhesive tape of the invention for producing repulpable bonds.

The uses according to the invention preferably include the use of a pressure-sensitive adhesive of the invention and / or of an adhesive tape of the invention for producing bonds, at least one of the substrates to be bonded being paper. Both substrates to be bonded are particularly preferably paper. Preferred bonds in this context are, for example, the bond of papers that can be split in the z direction to paper rolls, which are used in particular for temporary roll closure; the production of permanent splices between two rolls of paper; Gluing white coated paper or paper filled with calcium carbonate, gluing paper to a roll core (core starting) and fixing the outer paper layer of a paper roll (end tabbing).

Examples

Measurement methods

Gel permeation chromatography (GPC, measurement method A):

The details of number-average and weight-average molecular weights M _n , M _w in this document relate to the determination by gel permeation chromatography.

The determination is carried out on 100 µL clear-filtered sample (sample concentration 0.5 g / L). Tetrahydrofuran with 0.1% by volume of trifluoroacetic acid is used as the eluent. The measurement takes place at 25 ° C. A column type PSS-SDV, 10 µm, ID 8.0 mm x 50 mm is used as the guard column. PSS-SDV, 5 µm, 10 ³ Å (SN9090201) and 5 µm, 10 ² Å (SN9090200) columns, each with an ID of 8.0 mm, are used for separation. 300 mm (columns from Polymer Standards Service; detection using a PSS-SECurity 1260 RID differential refractometer). The flow rate is 0.5 mL per minute. The calibration is carried out against PMMA standards (polymethyl methacrylate calibration).

Determination of repulpability according to Tappi UM 213 (measurement method B):

“Fluffed pulp” (Co. Machery-Nagel MN 270, 270 g / m ² ) was used as the test paper.

A three-layer composite was produced by gluing the test paper over the entire surface on both sides with the adhesive to be tested. The samples prepared in this way were cut into 13 × 13 mm pieces and were filled with test paper pieces of the same size in a beaker up to a weight of 15 g.

The samples were placed in a mixer (Waring Blender Model 34BL47) with 500 ml of tap water.

Mixing was then carried out for 20 s at approx. 15,000 rpm. The mixer was then stopped and scraps of paper from the edges of the mixer were washed back into the pulp with tap water. This was repeated twice so that a total mixing time of 60 s was achieved. The pulp thus obtained was referred to as pulp 1.

All of the pulp 1 was placed in a disperger in which 2 l of tap water had been placed. It was rinsed with tap water in order to transfer the pulp 1 without leaving any residue. The disperger was then made up to 5 liters with tap water. It was dispersed for 1 min, then five beakers were filled with 770 ml each of the pulp 1 diluted in this way, of which the first, third and fifth were used to produce test sheets.

For this purpose, the contents of a beaker were placed in a cylinder and made up to 7 liters with tap water. Then air was blown through for 20 s and a waiting time of 20 s was observed in order to allow the foam to settle and allow the fibers to self-orientate. The water was then sucked off through a sieve let into the bottom of the cylinder and a vacuum was then applied for 1 min.

The freshly produced sheet was covered with a cover cardboard (chromo replacement cardboard, 240 mm diameter, Estanit) (smooth side below) and rolled over with a 2 kg steel roller. The resulting composite was removed and the free side covered with a cover paper (paper B13-c, 205 mm diameter, Estanit). This composite was dried in a dryer at 100 ° C. and under vacuum for about 5 minutes.

After drying, the cardboard boxes were carefully peeled off and the test sheet examined for fiber tears. A fiber tear indicates residual tack, which is caused by insufficient repulpability of the adhesive. Ideally, the cardboard boxes can be removed easily and the test sheet has two completely smooth sides. A slight fiber tear was still considered sufficient.

The test sheet was also examined for particles (specks) in both transmitted and reflected light. In order to pass the test, no particles were allowed to be visible on the test sheet.

"Repulpable yes / no" was recorded as the test result.

Adhesive strength (measurement method C):

The bond strength was determined at 23 ° C. +/- 1 ° C. temperature and 50% +/- 5% rel. Humidity.

The paper substrates used were previously stored permanently in the test climate.

• - Etikettenpapier Raflatac 1600.9, verklebt auf einer planen PE-Platte;
• - CaCO₃-haltiges Papier: MediaPrint Silk 250 g, Stora Enso Uetersen, 100 % CaCO₃ im Strich; auf einer PE-Platte mit tesa^®4965 fixiert;
• - Tapetenoberpapier 44540, 90 g/m², Koehler SE; auf einer PE-Platte mit tesa^®4965 fixiert.

The following paper substrates were used:

• - Raflatac 1600.9 label paper, glued to a flat PE sheet;
• - CaCO ₃ -containing paper: MediaPrint Silk 250 g, Stora Enso Uetersen, 100% CaCO ₃ in the coating; fixed on a PE plate with tesa ^® 4965;
• - Wallpaper top paper 44540, 90 g / m ² , Koehler SE; fixed on a PE plate with tesa ^® 4965.

• - sofort und
• - bei der Messung auf CaCO₃-haltigem Papier zusätzlich nach Lagerung der Verklebung für 3 d bei 40 °C/80 % relativer Feuchte und anschließend 20 h im Prüfklima

mit einer Geschwindigkeit von 300 mm/min und in einem Winkel von 180 ° vom Papiersubstrat abgezogen. Die dafür benötigte Kraft wurde dabei mit einer Zugprüfmaschine gemessen. Die Messergebnisse sind in N/cm angegeben und sind gemittelt aus drei Messungen.A 20 mm wide and 250 mm long strip of the adhesive to be examined was applied to the paper in question. The pressure-sensitive adhesive strip was pressed onto the substrate twice with a contact pressure corresponding to a weight of 2 kg. The adhesive to be examined was then

• - immediately and
• - When measuring on CaCO ₃ -containing paper, additionally after storage of the bond for 3 days at 40 ° C / 80% relative humidity and then for 20 h in the test climate

peeled off the paper substrate at a speed of 300 mm / min and at an angle of 180 °. The force required for this was measured with a tensile testing machine. The measurement results are given in N / cm and are averaged from three measurements.

Splitting force (measurement method D):

This test determines the splitting strength of a paper in the z-direction. The splitting strength or splitting force is the force that is necessary to split the paper body in the z-direction.

• - sofort sowie
• - nach Lagerung des Prüfkörpers für 1 Monat bei 40 °C und 80 % relativer Feuchte

durchgeführt.The adhesive to be examined was applied on both sides by initially painting with the finger to avoid air inclusions and then rolling it over twice with a hand roller on a split paper (paper that can be split in the z-direction, 69 µm, 73 g / m ² , splitting work <30 cN / cm) upset. This bond was produced in such a way that on one side the ends of the adhesive strip protruded beyond the test specimen and could be bonded onto itself with folds to form a handle. The measurements were

• - immediately as well
• - after storage of the test specimen for 1 month at 40 ° C and 80% relative humidity

carried out.

With a steel ruler, strips 15 mm wide and 20 cm long were cut out of the composite. The handles were pulled apart by hand until the paper was cracked.

The test specimen was clamped freely hanging from the handles above and below in a tensile testing machine and the strip was pulled apart at a speed of 300 mm / min (measuring climate 23 ° C., 50% relative humidity).

The force required for this was measured and is given in Table 2 as the mean value from five measurements.

Tack - Rolling Ball - Test (measurement method E):

In this test, a steel ball weighing 5.6 g rolled from a 65 mm high ramp onto a horizontal strip of the adhesive to be tested. The distance until the ball came to a standstill was measured (test climate 23 ° C, 50% relative humidity).

Before the measurement, the spheres were cleaned with cellulose and acetone and conditioned for 30 minutes in the open air in the test climate.

The adhesive was conditioned in the test climate for 1 day before the measurement.

Production of the adhesives:

A 300 L reactor conventional for free radical polymerizations was filled with a total of 100 kg of the monomers given in Table 1, corresponding to the composition also given there, and 72.4 kg of ethanol / water (70:30). After nitrogen gas had been passed through it for 45 minutes with stirring, the reactor was heated to 58 ° C. and 50 g of Vazo® 67 were added. The jacket temperature was then increased to 80.degree. C. and the reaction was carried out constantly at a jacket temperature of 70.degree. After a reaction time of 1 hour, another 50 g of Vazo® 67 were added. To reduce the residual initiators, another 50 g of Vazo® 67 were added after 6 hours. The reaction was terminated after a reaction time of 24 hours and the mixture was cooled to room temperature. The solution was adjusted to a solids content of 30% by weight. The crosslinker indicated in each case was then stirred in.

The composition obtained was coated in solution onto a siliconized PET film using a comma blade. The solvent was removed in a drying tunnel (20 min, 80 ° C.). The thus obtained Mass was than laminated to be tested adhesive onto a respective specified in the test methods backing, the coating weight was 50 g / cm ^2. Table 1: Composition of the adhesives No . Monomers (% by weight, based on the monomer composition) Crosslinker (% by weight, based on polymer) Acrylic acid 2-hydroxyethyl acryl at N, N-dimethylacrylamide Ethyl diglycol acrylate n-butyl acrylate Aluminum acetylacetonate Titanium diisopropoxide bis (acetyl acetonate) 1* 5 95 0.33 2 * 10 90 0.33 3 * 22nd 28 35 15th 0.33 4th 5 20th 75 0.33 5 5 30th 65 0.33 6th 10 10 80 0.33 7 * 10 90 2 8th* 20th 80 2 9 1 30th 69 2 10 3 20th 77 2 11 5 30th 65 3 12th 10 10 80 3 * - Comparative Example Table 2: Test Results No. Repulpability Adhesive strength (N / cm) Rolling Ball (mm) Splitting power Label paper CaCO ₃ paper (immediately / after storage) Wallpaper top paper right away after storage (1 month at 40 ° C / 80% relative humidity) 1* No 2 * No 3 * Yes 7.7 6.42 / 3.73 6.2 208 not determined not determined 4th Yes 7.8 7.0 / 7.0 8.2 56 29 27.2 5 Yes 8th 6.5 / 6.0 7.95 78 29.2 27.5 6th Yes 8.4 6.5 83 29.2 28.1 7 * No 8th* No 9 Yes 7.2 7.7 41 26.9 44.1 10 Yes 7th 7.2 9 30.2 37.6 11 Yes 7.3 8.5 / 7.9 8.8 80 29.3 33.8 12th Yes 6.3 6.9 34 29.3 33.6 * - comparative example

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2014/001096 A1 [0007]
• WO 9514746 A2 [0008]
• EP 0699726 A2 [0009]
• EP 1489153 A1 [0010]

Claims (7)

Pressure-sensitive adhesive comprising at least one polymer, the underlying monomer composition of which a) 10 to 30% by weight of at least one compound according to the formula (I) CH ₂ = CH-C (O) NR ¹ R ² (I), wherein R _{1 represents} an unsubstituted alkyl group, a hydroxyalkyl group or an acetonyl radical and R _{2 represents} a hydrogen atom, an unsubstituted alkyl group, a hydroxyalkyl group, an acetonyl radical or an aminoalkyl group; b) 60 to 80% by weight of at least one compound according to the formula (II) CH ₂ = CH-C (O) O- (CH ₂ ) ₂ -OR ³ (II), wherein R ^{3 represents} an unsubstituted alkyl group, an alkoxyalkyl group or a (polyalkoxy) alkyl group; and c) 0.5 to 10% by weight of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid and (C ₂ -C ₄ -hydroxyalkyl) acrylates. Pressure sensitive adhesive according to Claim 1 , characterized in that R ₁ and R ₂ independently represent an unsubstituted alkyl group. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that R ^{3 stands} for an ethyl group or an ethoxyethyl group. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomer composition comprises at least acrylic acid or 2-hydroxyethyl acrylate as monomer c). Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the polymer is thermally crosslinked. Adhesive tape comprising a pressure-sensitive adhesive according to any one of the preceding claims. Use of a pressure-sensitive adhesive according to one of the Claims 1 to 5 and / or an adhesive tape according to Claim 6 for the production of water-soluble bonds.